Instructions

1. Look carefully at the jar itself. Canning jars are made from glass, whereas modern freezer jars are manufactured with plastic. You can use glass canning jars for freezing, but you shouldn't use the plastic jars for canning.

2. Check the brand name. Common brands of canning jars include Ball, Kerr and Weck. Ball also now produces plastic freezer jars.

3. Examine the lids. Lids for canning jars often have two parts to ensure the proper seal: a flat metal disc and a round screw-on lid that you place on top of the disc. These are usually referred to as "lids and rings" or "lids and bands." In the case of Weck and some other jars, the band is rubber and the lid is glass.

4. Identify the shape and texture of the jar. Most canning jars are round, with traditional sides that don't vary in circumference, but don't rule out more shapely styles at first glance -- Weck jars offer more curves. You can identify Weck jars by their particular shapes, including tulip and deco styles, as well as juice jars and especially tall jars for canning asparagus. Similarly, Ball offers textured jars suitable for both canning and freezing; these are called "quilted crystal jelly jars."

5. Check for the combination of shape and material when you're identifying freezer jars. The plastic jars, such as those made by Ball, feature twist-on seal lids and a fill line. Plastic freezer containers also often include a fill line, but the lid simply snaps into place. Companies such as Ziploc also offer plastic freezer containers and bags, but not plastic jars.

6. Get familiar with the color-coding system. The Ball company developed a color-coding system to help consumers distinguish between freezer and canning jars. Ball jars in blue packages are freezer-safe. Their red boxes are for canning smaller fruits, and their green boxes are for canning larger fruits and vegetables.

7. Discard any jars with nicks or cracks for canning purposes. These imperfections prevent an airtight seal, which is necessary for canning jars.

8. Find a recipe or method based on whether you want to freeze or can to take the next step and actually preserve your food. Follow instructions carefully, which vary based on type of food. (see Resources) Store your preserved food. With a particularly bountiful harvest, you can even give preserved food in pretty jars as gifts to friends, neighbors and family.